AJOYE Or, Ajoie; Elsgau (Ger).
Carolingian district between the Jura and the Vosges, now divided between eastern France and northwestern Switzerland.
In the 11th century, westernmost Ajoye lay in the northeast of the County of Burgundy, where it remained. The rest of the district came into the hands of Louis of Mousson c.1036, and was divided between two of his grandsons in 1104 into the Counties of MONTBÉLIARD and FERRETTE (the latter later became associated with the County of Sundgau in Upper Alsace).
The district around Porrentruy, once part of Montbéliard, was sold to the Bishop of Basle in 1271 and the town later became his residence. In 1793 the Porrentruy distrct became French. In 1815 they were included in the Swiss Canton of Bern, but they now form the northwest of the Swiss Canton of Jura.